The generation and use of transgenic and gene-targeted mice has become an essential technology for basic cancer research, as well as for other areas of basic biomedical research. Therefore, this facility serves two critical functions within the Cancer Center. First, the Animal Facility provides convenient, affordable and high quality animal care and maintenance to Cancer Center investigators who use transgenic, mutant and other experimental mice in their research. The support for this Facility provided by the Cancer Center, as well as by the University, results in animal maintenance charges that are relatively affordable, which is a prerequisite for genetic studies using large numbers of transgenic and mutant mice. Second, the Facility operates a transgenic and chimeric mouse production service, which allows all Cancer Center investigators to generate new strains of transgenic mice or perform gene targeting (e.g., gene knockout) studies. The Facility provides technical advice on the design and construction of transgenes and gene-targeting vectors. DNA constructs for transgenesis, and genetically modified ES cell lines are produced by individual Cancer Center investigators, then delivered to the facility, where they are injected into mouse eggs or blastocysts, respectively. The resulting mice are then returned to the individual investigators for further analysis and breeding. The Facility also plans to provide cryopreservation of mouse embryos, and to produce new wild type ES cell lines for use by investigators.